Subscription resolvers in GraphQL - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a subscription resolver that listens for new messages.

GraphQL

const resolvers = {
  Subscription: {
    newMessage: {
      subscribe: [1]
    }
  }
};

Drag options to blanks, or click blank then click option'

Apubsub.listen('NEW_MESSAGE')

Bpubsub.publish('NEW_MESSAGE')

Cpubsub.subscribe('NEW_MESSAGE')

Dpubsub.asyncIterator('NEW_MESSAGE')

Attempts:

3 left

💡 Hint

Common Mistakes

Using pubsub.publish instead of asyncIterator

Calling a non-existent pubsub.listen method

The subscribe function must return an async iterator from pubsub.asyncIterator to listen for events.

2fill in blank

medium

Complete the code to publish a new message event after saving the message.

GraphQL

async function sendMessage(message) {
  await saveMessageToDB(message);
  pubsub.[1]('NEW_MESSAGE', { newMessage: message });
}

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Asubscribe

BasyncIterator

Cpublish

Dlisten

Attempts:

3 left

💡 Hint

Common Mistakes

Using subscribe instead of publish

Trying to call asyncIterator to send events

To notify subscribers, use pubsub.publish with the event name and payload.

3fill in blank

hard

Fix the error in the subscription resolver to correctly return the async iterator.

GraphQL

Subscription: {
  messageAdded: {
    subscribe() {
      return pubsub.[1]('MESSAGE_ADDED');
    }
  }
}

Drag options to blanks, or click blank then click option'

AasyncIterator

Bpublish

Csubscribe

Dlisten

Attempts:

3 left

💡 Hint

Common Mistakes

Returning pubsub.publish instead of asyncIterator

Using a non-existent listen method

The resolver must return pubsub.asyncIterator to create an async iterator for the subscription.

4fill in blank

hard

Fill both blanks to create a subscription resolver that filters messages by channel.

GraphQL

Subscription: {
  messageByChannel: {
    subscribe: withFilter(
      () => pubsub.[1]('MESSAGE_SENT'),
      (payload, variables) => payload.channelId [2] variables.channelId
    )
  }
}

Drag options to blanks, or click blank then click option'

AasyncIterator

B===

C!==

Dpublish

Attempts:

3 left

💡 Hint

Common Mistakes

Using publish instead of asyncIterator

Using !== instead of === in the filter

Use pubsub.asyncIterator to listen for events and === to filter messages matching the channel ID.

5fill in blank

hard

Fill all three blanks to define a subscription resolver with a filter and a custom resolve function.

GraphQL

Subscription: {
  commentAdded: {
    subscribe: withFilter(
      () => pubsub.[1]('COMMENT_ADDED'),
      (payload, variables) => payload.postId [2] variables.postId
    ),
    resolve: (payload) => payload.[3]
  }
}

Drag options to blanks, or click blank then click option'

AasyncIterator

B===

Ccomment

Dpublish

Attempts:

3 left

💡 Hint

Common Mistakes

Using publish instead of asyncIterator

Using !== instead of === in filter

Returning wrong property in resolve

The subscription uses asyncIterator to listen, === to filter by postId, and the resolve function returns the comment from the payload.